The present invention relates to earphones, a large variety of which have been proposed in the art. The prior art earphones are generally classified into types shown in FIGS. 1(a) to (d) according to the manner in which they are attached to the ear. FIG. 1(a) shows a pair of earphones in a headphone arrangement. The headphone is made up of a pair of speaker units 1, a head band 2 coupling the speaker units 1, and a cord 3 through which electrical signals are supplied to the speaker units 1. The head band 2 has a resiliency so as to fit the speaker units 1 to the user's ears. Due to the head band 2, a rather great pressure may be applied to the user's temples or the external ears or pinnae. Also, with such a construction, since the speaker units 1 are fitted on the external ears or pinnae, each speaker unit 1 is far from the external meatus of the ear canal and the space defined therebetween is rather large. Therefore, only part of the acoustic energy emanating from each speaker unit 1 is supplied into the ear canal while remainder is leaked, thereby decreasing the efficiency of the headphone.
Due to the presence of the acoustic chamber defined by the speaker unit 1 and the external ear, sound reflected from the surface of the external ear and the unit results in a degradation of acoustic characteristics. For this reason, it is difficult to provide high performance headphones of this type.
FIG. 1(b) shows a so-called ear hook type earphone. The ear hook type is made up of a speaker unit 1, an ear suspension loop 12 formed integrally with the unit 1 and a cord 3 through which electrical signals are supplied. The earphone thus constructed is hooked around the external ear or pinna to hold the unit 1. However, the fit thus provided is not stable and it is difficult to attach and detach the earphone from the external ear. Furthermore, in this type, the unit 1 is in contact with the external ear or positioned in the vicinity of the external ear. For the same reason as in the above described headphone, this earphone is inferior in acoustic characteristics.
FIG. 1(c) shows a "stethophone" type earphone set. It is composed of a pair of speaker units 1, a band 2 in the form of a stethoscope and a cord 3 through which electrical signals are supplied. The units 1 are held close to the external ears or pinnae with a pair of projected acoustic tubes 4 held in contact with parts of the external ears or pinnae by the resilient force of the band 3.
FIG. 1(d) shows an earphone which is composed of a speaker unit 1, an ear plug 5 extending from a front surface of the unit 1 and a cord 3 through which electrical signals are supplied. The ear plug 5 serving as an acoustic tube is inserted into the external auditory meatus.
The fit obtained with the devices shown in FIGS. 1(c) and (d) is not stable and these earphones are all easily pulled away from the user's ears. Moreover, in the known devices as shown in FIGS. 1(c) and (d), generated sounds are propagated via acoustic tubes. Such a construction cannot provide desirable acoustic characteristics.
FIG. 1(e) shows a prior art headphone wherein a speaker unit is composed of a magnetic circuit 60 having a magnetic gap 60a, a vibrating diaphragm 61 having a voice coil 61a and a frame 63 to which the magnetic circuit 60 is directly secured and to which the diaphragm 61 is secured through a ring 62. The speaker unit is encased and secured in a protective case 64 made up of a body 64a and a cover 64b. An ear pad 65 is attached to a sound hole 64b' of the cover 64b. Sound absorbing material 66 is attached to the bottom of the body 64a. Reference numeral 63a denotes sound holes formed in the frame 63.
Since in the prior art headphone shown in FIG. 1(e), the outer periphery of the frame in which the diaphragm is provided is secured to the inner periphery of the body of the case to thereby fix the speaker unit at a desired predetermined position and then the cover 64b is attached to the outer periphery of the body, the outer diameter of the case is considerably large in comparison with the diameter of the diaphragm. The space use efficiency thereof is inferior. With such a construction, it is very difficult to miniaturize the ear speaker.
As described above, the various types of known ear speakers cannot simultaneously satisfy both compactness and high performance requirements.
In view of the above noted defects inherent to the prior art techniques it is an object of the present invention to provide a novel ear speaker with compactness and high performance.